Multiple anode tube and method of employing the same in testing apparatus



OYING INVENTOR. IVAN LOJOYQ BY ATTORNEY EJF" - l. L. JOY MULTIPLE ANODETUBE AND METHOD OF EMPL Filed Aug. 4, 1945 THE SAME IN TESTING APPARATUSOct. 31, 1950 Patented Oct. 31, 1950 MULTIPLE ANODE TUBE AND METHOD OFEMPLOYING THE SAME IN TESTING AP- PARATUS Ivan L. Joy, Topeka, Kans.

Application August 4, 1945, Serial No. 608,950

This invention relates to electrical testing equipment of the characteremployed in determining the presence of flaws or faults in materialcapable of conducting an electrical'current 'or being magnetized.

The primary object of my invention is to provide anelectron tube havingspecial structure and characteristics and therefore, desirable for usein treating apparatus of the character just above set forth. r

A further aim of this invention is the provision of a multiple anodetube for testing apparatus, which tube has anodes arranged in balancedpositions with respect to its cathode. This tube is also provided withguide plates or other members, functioning to confine the flow ofelectron'to the anodes in a uniform fashion.

Further aims of this invention include the provision of an electron tubefor use as a part of a system for testing material, which tube has atleast two pairs of anodes, the anodes of each pair being disposed inopposed relation and with respect to a cathode. Cooperating with theanodes are guiding means to insure even flow of electrons, to the endthat deflection of the electrons passing to the anodes will cause agreater reaction at the anodes. Such reaction is due to varying magneticlines of flux and this arrangement will, therefore, render the entiretube more sensitive Still further objects of the inventionare to providean electron tube having at least fouranodes therein; to provide such atube with a centrally disposed cathode serving all of the anodes, whichanodes are of identical size and 2 Claims. (01. 250-27.5)

angularity with respect to the cathode; to provide a tube having anodesthat cooperate with non-energized guide means forelectrons toconcentrate the latter, and therefore, render the action of the tubemore responsive to relatively slight variations in the magnetic lines offorce. It'is through the medium of such variations that the character ofthe material being tested is determined.

Other objects of the invention will appeardur- Fig. 3 is a view similarto Fig. 2, but with guide plates in the envelope of the tube for guidingthe flow of electrons from the cathode to the anodes.

Fig. 4 is a view similar to Fig. 3, but illustrating the presence ofmagnetic lines of force thatdefleet the electron flow. i

Fig. 5 is a similar view showing how the magnetic lines of force fromthe material being tested, have no effect upon the electron fiow if nodefect or fault is present.

Fig. 6 is a view similar to Fig. 5, but indicating the manner in which aflaw will effect the how of electrons to at least one of the anodes.

Fig. 7 illustrates the manner in which the tube made in accordance withthis invention, may be passed through a magnetic field in certainpositions with respect thereto without changing the electron flow.

Fig. 8 illustrates the four-anode-tube in a cir' cuit capable ofoperating the tube in apparatus where testing for faults is the primeobjective;

and

Fig. 9 is a vertical cross sectional view of-the multiple anode tubetaken on line IXIX of Fig. 7.

Testing apparatus with which the tube made as illustrated isparticularly useful, is that for determining flaws in rails. Obviously,the tube is usable where it is desirable to determine the presence offaults in any magnetizable substance; but for purpose of clarification,reference will hereinafterbe made to the multiple anode tube as being apart of testing equipment in the nature ofthat illustrated in U. S.Letters Patent No. 2,030,101, dated February 11,1936. This example isset down merely to reveal to one skilled in the art, the type ofequipment wherein the multiple anode tube made pursuant tothisinvention, may be included. In that said patent, the housing 2|could carry three or four tubes of the character illustrated in Fig. 8of the accompanying drawing. If such a tube is used in the testingapparatus, its variable sensitivity will suit any field strength and itsself-balancing characteristics renders it unnecessary to usephasingamplific'a tion. The material being tested can be analyzed to a pointvery near its ends and the relatively small size of the tubes makes itpractical to arrange them to pick up or be affected by lines of forcemoving in all directions. Thus, all types of defects may be detected.

Cathode ray tubes cannot be made small enough to be practical in theinterception of magnetic fields'being tested. When such tubes are used,it is necessary to employ at least six to locate all types of defects.Even if itwere pos sible to dispose cathode ray tubes in the propermanner for efficient testing as contemplated by this invention, and asis possible through the use of my multiple anode tube, it would benecessary to use phasing amplification to balance out the currentintensity variations, and this would be impractical as the amplifierswould have to be perfectly linear.

The answer to the problem is the small, fouranode balanced tube of thecharacter diagrammatically shown in the drawing, wherein the numeral IEIdesignates an envelope, substantially cylindrical in form and mountedupon a base of well-known type for inclusion in a circuit.

The envelope has an electron emitting cathode l2 and a grid M atsubstantially the axis of its enclosed space, and the anodes l6, I8, 2%and 22 are positioned as shown inall of the views. These anodes areconcentric with cathode l2 and are balanced with respect to theirposition to insure a bi-lateral sensitivity pattern which is the primeasset of the tube.

Guide plates 24 and 25 disposed in spaced apart relation and to eachside of cathode l2, serve to guide the electron flow to anodes l6, I8,26 and 22, as illustrated in Figs. 2 to 7 inclusive. If these platesZwere not present, the electron flow would be of a patterndiagrammatically shown in Fig. 2. When most of the space within envelope[0 between the anodes filled with guide plates 24 and 26 as in Fig. 3, aconcentrated uniform flow is effected by the magnetic lines of forcethrough which the tube is passed when the testing apparatus is in use.

There is no potential applied to plates 24 and 26. The anode voltage isprovided through conductors 28, 38, 32 and 34 joined to anodes l6, i8,20 and 22 respectively. This voltage is applied to the amplifier throughconductor 36, having a condenser 31 interposed therein, where meterswill indicate the flow of electrons and any deflection thereof thatmight be caused by a deviation in the magnetic lines of force due to afiaw or fault in the material being tested. Obviously, it is known thatthe tubes made as illustrated are moved through magnetic lines of fluxdesignated by the numeral 38 in Fig. 5, where no deflection thereof isoccurring. The rail 46 is, in this instance, the article being tested,and it is energized as set forth in the above identified U. S. LettersPatent, to the end that said magnetic lines of flux 38, may be created.

A flaw 42 is schematically illustrated in Fig. 6.. This flaw appears inthe rail 49 and as a result thereof, the magnetic lines of fiuX 44 aredeflected to effect the flow of electrons to anode 18. Current isapplied to spaced apart points on rail 40, and it is between thesepoints that a number of the tubes made as illustrated, are disposed,This electro-inductive method of testing is highly successful but ismade more so by the use of the multiple anode tube, especially becausewhen the tubes are so placed as to cause the anodes l5, I8,

"20 and 22 thereof to intersect the straight lines of flux, anydeviation from the straight line is more accurately reflected andmeasurable.

As defect 42 progresses by the tube, the reaction will be indicated onthe tape of a conventional chronograph. current induced into rail 48will fluctuate as the lengths thereof change between the points ofcontact of the input current. This fluctuation is balanced out withinthe tube circuit shown in Fig. 8.

When the defect 42 is directly below cathode l2 It must be assumed that;

for an instant, potential at anodes IE and 20 assume normal value thesame as when no defect is near. Now, when the defect 42 is causing adeflection of magnetic lines of flux nearest anode i8, as shown in Fig.6, the electrons flow from cathode [2 to anode I8 is decreased due tothe fact thatthe lines of flux change the electron flow in directproportion to the strength of flux and potential applied to the anodel8. The electrons are moved to cause a greater flow of electrons towardanode Hi. This varied potential results in lowering the potential atanode l6 and raising the potential on anode l8thus, implying changedpotential at conductors 34 and 32 respectively. This potential is higherin conductor 32 and is amplified by passing to conventional currentamplifiers through conductor 36. The amplified current is used tooperate the chronograph to indicate the presence of flaw 42.

The action just set forth occurs twice-once when the flaw 42 passesnearest anode l8, and once when it passes nearest anode 22.

Contrary to the potential variation as just set forth when flaw 42 isnearest anode l8, the potential when'fiaw 42 is nearest anode 22 will belower at anode 20 and therefore, lower in conductor 32. By using properamplifiers, it is possible to amplify potential variations in bothdirections to produce chronographic variations when the flaw 42 passesboth anode l8 and anode 22.

Anodes l6 and 22 are connected in parallel by conductor 28 and anodes I3and 20 are connected in parallel by conductor 30. Both conductors 3D and32 are connected to Output 36 leading to the amplifying system.

Source of current 46 is connected to cathode l2 by conductors 48 and 58from one pole of a battery having suitable output. The other pole ofbattery 46 is connected to the anodes l6, l8, 2!] and 22 throughresistors 52 and 54. These resistors 52 and 54 are used to allow thepotentials at the said anodes to vary in accordance with the duration ofthe magnetic lines of force due to presence of a flaw.

The voltage on the grid is adjusted to a point .at which the electronflow is correct to allow efiicient operation of the tube. This voltageis adjusted through employment of potentiometer 56 connected to grid 14by wire 58.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. An electron tube comprising an envelope; an electron emanatingcathode in said envelope; a plurality of anodes disposed within theenvelope in a circular pattern around said cathode, whereby to present abalanced electron flow within the envelope when the cathode is disposedin a magnetic field with the current flow of the magnetic fieldsubstantially parallel to said electron flow; and uncharged plateswithin the envelope for guiding the electrons toward the anodes, saidplates being mounted parallel to and outside the normal electron flowtoward the anodes.

2. An electron tube comprising an envelope; an electron emanatingcathode in said envelope; a plurality of anodes disposed within theenvelope in a circular pattern around said cathode, whereby to present abalanced electron flow within the envelopewhen the cathode is disposedin a magnetic field with the current flow of the magnetic fieldsubstantially parallel to said electron flow; and uncharged plateswithin the envelope for developing electrons outside the normal flowthereof toward the anodes, said plates being disposed parallel to andoutside said normal flow of electrons, whereby to confine the electronsto a substantially rectangular space defined by the IVAN L. JOY.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number 6 UNITED STATES PATENTS Name Date Holliday Jan. 20, 1931 ThompsonMar. 29, 1932 Fritz Oct. 11, 1938 Lopp Mar. 28, 1939 Fritz May 16, 1939Barnes et al July 4, 1939 Van Overbeek et al. July 25, 1939 Okabe Jan.16, 1940' Skellett Oct. 15, 1940

